Bolyai Society Mathematical Studies

Abstract: Access to clean air, a vital necessity for life, faces severe constraints globally due to industrialization and urbanization, leading to widespread air quality deterioration. To safeguard human health and the environment from detrimental effects, the essential components of proper monitoring, assessment, and management of air quality are paramount. Conventional air quality analytical techniques such as gas chromatography/ mass spectrometry, selected ion flow tube mass spectrometry, thermal desorption/ gas chromatography, and mass spectrometry are widely used for air quality analysis. These methods, however, are laborious, necessitate sample preparation, require expansive and hazardous reagents, and have a high cost of equipment and maintenance. As such, more rapid, sensitive, specific, cost-effective, portable, user-friendly, and environmentally friendly analytical tools are required for efficient air quality monitoring and control. Over the years, various techniques have emerged to address these challenges, including mobile sensors, microbial monitoring, the Internet of Things (IoT), biomonitoring, and bio- and nanosensors in both indoor and outdoor settings. This paper offers an overview of recent advancements in air quality monitoring and assessment methods. The review encompasses sample preparations for air pollutants, data analysis methodologies, and monitoring strategies. It also delves into the crucial role of microorganisms in air quality analysis. Additionally, the paper explores the applications of the Internet of Things (IoT) and biosensors in air quality monitoring and assessment, elucidating their roles in advancing these endeavors. The paper concludes by presenting insightful perspectives on the current state of air quality monitoring techniques and outlining future directions for research and development in this critical field.

Abstract:: In recent years, research and development efforts have been heavily focused on conductive diamond electrodes for electrochemical applications. Such initiatives may have been spurred by their broad potential window, low background current, chemical inertness, and mechanical robustness. Compared to other carbon-based materials, conducting diamond can oxidize several analytes before the breakdown of water in aqueous electrolytes. Since the evolution of oxygen and hydrogen does not obstruct the analysis, this is significant for the detection and/or identification of species in solution. As a result, conductive diamond electrodes expand the application of electrochemical detection and make it possible to use them for analytes that are incompatible with traditional electrode materials. Fabricating boron-doped diamond films via chemical vapor deposition on different substrates is of special interest. This article highlights the therapeutic and electroanalytical applications of boron-doped diamond electrodes in various aspects in addition to the synthetic strategies to obtain Boron Doped Diamond Electrodes (BDDE), the cost-effectiveness of BDD and its in-vivo compatibility that will help the analytical researchers to learn almost everything about the previous studies done on BDDE and encourage them to work more efficiently in this research field.

A new material of SiO<sub>2</sub>-(1-(bis(2-aminoethyl)amino)-3-(silyl)propane-2-ol) (SiO<sub>2</sub>- BAEASP) has been successfully synthesized as a promising SiO<sub>2</sub>-based material for the filtration and capturing UO<sub>2</sub> <sup>2+</sup> ions. In this study, the chemical structure and possible uses of SiO<sub>2</sub>-BAEASP in environmental remediation are explored. Moreover, the methodologies and procedures for synthesizing and characterizing SiO<sub>2</sub>-BAEASP are also described. In addition, the experimental methodologies regarding the capturing capacity, pH, initial concentrations, and temperature dependence are determined. The FT-IR spectra of SiO<sub>2</sub>-BAEASP materials show distinct functional groups, including the disappearance of ν<sub>Si–O–H</sub> stretching vibrations and the appearance of sharp ν<sub>Si–O–Si</sub> vibrations. However, detection of the primary and secondary amine stretching frequencies at 3251 cm-1 becomes difficult when it is chelated with UO<sub>2</sub><sup>2+</sup> ions due to its weak density and interference with the –OH stretching frequency. Thermogravimetric analysis (TGA) and weight loss patterns for SiO<sub>2</sub>-BAEASP before and after capturing UO<sub>2</sub><sup>2+</sup> ions suggest the formation of coordination complexes between UO<sub>2</sub><sup>2+</sup> ions and organic functional groups, impacting the thermal properties of the material. Furthermore, the Powder X-ray Diffraction (PXRD) spectrum indicates that the atomic arrangement within the crystals of the material remains largely unchanged before or after adsorption, suggesting that the adsorption of uranyl ions is likely to occur predominantly on the material's surface, with limited impact on the bulk structure. The SEM shows an increase in surface roughness or the formation of layers of nano-spherical particles on the surface, forming clusters or agglomerations. The maximal capturing capability of UO<sub>2</sub><sup>2+</sup> ions into SiO<sub>2</sub>-BAEASP is 99% under the experimental circumstances of pH = 5 - 7, C<sub>i</sub> = 50 mg L<sup>-1</sup>, T = 55°C, dosage = 2 g L<sup>-1</sup>, and 80 rpm. The capturing of uranyl ions follows the Langmuir isotherm model (R<sup>2</sup> ≈ 1) as a favorable process (<i>R<sub>l</sub></i> < 0.02). The capturing process has ΔG = − 8.2083 to -16.0568 kJ mol<sup>-1</sup>, ΔH (+69.7927 kJ mol−1), and ΔS (+2.616166 kJ mol<sup>-1</sup> K<sup>-1</sup>), which indicates that the adsorption is energy-efficient and spontaneous. The pseudo-secondorder and Weber-Morris intraparticle diffusion models (ca. <i>R<sup>2</sup></i> = 1.0) suggest that the capturing mechanism follows chemisorption through three distinct stages of sorption, indicating that intraparticle diffusion primarily governs the transport of UO<sub>2</sub><sup>2+</sup> ions into the SiO<sub>2</sub>-BAEASP. The main findings confirm the ability of SiO<sub>2</sub>-BAEASP to trap UO<sub>2</sub><sup>2+</sup> ions in contaminated fluids efficiently and its importance in environmental remediation and resource recovery.

Abstract: Nanoplastics (NPs) have emerged as a concerning environmental pollutant due to their ubiquitous presence and potential adverse effects on human health. This review aims to elucidate the routes of NP contamination and their associated toxic effects on various systems within the human body. The inhalation of NPs presents a significant route of exposure, where particles can deposit deep within the respiratory tract, leading to potential respiratory health complications. Similarly, ingestion of NPs through contaminated food and water sources poses a risk to gastrointestinal and urinary tract health. Additionally, dermal permeation of NPs highlights another avenue for exposure, raising concerns about skin health. The potential toxic effects of micro(nano)plastics (MNPs) on human health span across multiple physiological systems. MNPs have been implicated in respiratory ailments, gastrointestinal disturbances, cardiovascular complications, blood abnormalities, compromised immune responses, neurological impairments, and reproductive dysfunctions. Understanding these toxic effects is crucial for developing strategies to mitigate NP exposure and protect human health. This review underscores the urgent need for interdisciplinary research efforts aimed at assessing NP toxicity comprehensively and implementing measures to reduce NP contamination in the environment.

Aim: The ashlar belongs to a classic palace located in the city of Milan (Italy), built in 1883 by a renowned architect of the time. It was studied in detail in order to establish the material it is made of and to highlight its degradation and what caused it. Methods: The study was carried out by combining different techniques, for example, a detailed minero-petrographic study was performed, together with classical chemical qualitative and quantitative analyses of all the main cations and anions present, using ion chromatography and UV-Vis spectrophotometry. On the other hand, most of the classic instrumental analytical methodologies were also performed, such as powder X-ray diffractometry, thermal analysis (TG, DTG, and DTA), and SEM spectroscopy. Results: In this way, it was possible to know its composition, hypothesize the origin of the material, highlight the type of degradation, and study the main likely causes. Conclusion: The focus of the research, in our opinion, lies both in the scarcity of published studies regarding this type of artefact, especially if it belongs to the period of the artefact we investigated, and in having demonstrated how chemical and instrumental analyses of different types, can contribute to obtaining different information and how, above all, their results are useful for the mutual validation of the results themselves.

Background: The present study is focused on the collection of honey samples from the different geographical and climatic conditions of Khyber Pakhtunkhwa and analyzing them for the determination of riboflavin. Quantification of riboflavin, being natively fluorescent, was accomplished using spectrofluorimetric method. Riboflavin has characteristic fluorescence spectra with maximum excitation at 464 nm followed by an emission peak at 525 nm. Method: The procedure followed in this work comprised the construction of a calibration curve by plotting the fluorescence intensity of a series of riboflavin solutions versus concentration. This curve was used for the quantification of riboflavin in the collected honey samples. The effect of several external factors such as the altitude of the sampling area, type of honey bee, type of flowers from which the nectar was collected, and sampling season on the concentration of riboflavin in the honey samples was statistically evaluated. Results and Discussion: It was concluded that the samples collected from lower altitudes have high concentrations (1.156±0.08 μg g-1) of riboflavin. Similarly, the samples collected in autumn were found to have a maximum average riboflavin concentration of 1.37±0.06 μg g-1, which was higher in comparison to the samples collected in other seasons of the year. Likewise, the effect of flora on the concentration of riboflavin was also investigated and it was found that honey samples collected from areas where the nectar was collected from Ziziphus contains maximum riboflavin concentration averaged at 1.383±0.1 μg g-1. Conclusion: Based on the size of the honey bees, the samples collected from hives of small honey bees were found to have a maximum riboflavin concentration of 1.176±0.07 μg g-1. This study suggests that besides the studied vitamin, the rest of the vitamins and other nutritional components may vary in the honey samples depending upon external factors. conclusion: It was concluded that the samples collected from lower altitudes have high concentration (1.156±0.08 μg g-1) of riboflavin. Similarly, the samples collected in autumn were found to have a with a maximum average riboflavin concentration of 1.37±0.06 μg g-1, which was higher in comparison to the samples collected in other seasons of the year. Likewise, the effect of flora on the concentration of riboflavin was also investigated and it was found that honey samples collected from areas where the nectar was collected from Ziziphus contains maximum riboflavin concentration averaged at 1.383±0.1 μg g-1. Based on the size of the honey bees the samples collected from hives of small honey bees were found to have maximum riboflavin concentration of 1.176±0.07 μg g-1. This study suggests that beside the studied vitamin, the rest of the vitamins and other nutritional components may vary in the honey samples depending upon external factors.

Background: L-cysteine (L-CySH) plays a crucial physiological role in the life-support system, which has been widely applied in the food and medicine industries. Abnormal content of LCySH in the human body can lead to liver damage, Alzheimer's disease, and even cancer. Therefore, it is of great practical importance to investigate highly sensitive and selective methods for the determination of L-CySH. Methods: L-CySH electrochemical detection by cyclic voltammetry (CV) technique was reported using the polyaniline/BiPr composite nanosheet-modified glassy carbon electrode (GCE). objective: Polyaniline/BiPr composite nanosheets modified glassy carbon electrode (GCE) was used for L-cysteine (L-CySH) electrochemical detection by cyclic voltammetry (CV) technique. Results: The obtained nanosheets with a size of less than 500 nm were composed of rhombohedral Bi1.35Pr0.65O3, tetragonal Bi2O3, and hexagonal Pr2O3. Irregular polyaniline nanoparticles were covered on BiPr nanosheets. Polyaniline/BiPr composite nanosheet-modified GCE had good electrocatalytic performance for L-CySH detection. A pair of CV peaks was observed on the BiPr composite nanosheet-modified GCE with the potentials at +0.06 V and –0.75 V. Peak potentials at the polyaniline/ BiPr composite nanosheet-modified GCE were shifted to –0.09 V and –0.72 V. The linear range detection limit indicated 0.0005–2 mM and 0.086 μM for the polyaniline/BiPr composite nanosheet-modified GCE. Conclusion: Polyaniline/BiPr composite nanosheets provide a kind of new electrode material for improving the electrochemical performance towards L-CySH determination.

Background: The gaseous detonation method is a promising method for the rapid and large-scale preparation of graphene quantum dots (GQDs). However, the relationship between detonation parameters and the morphological and optical properties of GQDs remains unclear and needs further investigation. Methods: This study systematically investigates the influence of detonation parameters— specifically, the initial temperature, molar ratio of H2 to O2, and the amount of the precursor (benzoic acid, BA)—on the morphological and optical properties of GQDs. An orthogonal experiment was conducted with initial temperature, H2 to O2 molar ratio, the amount of BA as factors, and particle size, crystallinity, and photoluminescence quantum yield (PLQY) as indicators. Results: Findings indicate that increasing the initial temperature and the molar ratio of H2 to O2 increases the particle size, crystallinity, and PLQY of the GQDs. In contrast, the amount of BA has minimal influence on these properties. Additionally, detonation parameters had no significant effect on the group types, ultraviolet-visible (UV-vis) absorption, and photoluminescence (PL) emission spectra of GQDs. The optimal preparation conditions are when the initial temperature T0 is 393.15 K, the molar ratio of H2 to O2 is 2:1, the amount of BA is 4 g, and the PLQY of the prepared GQDs is maximized. Conclusion: By altering the detonation parameters, the particle size, crystallinity, and PLQY of GQDs can be finely controlled. These findings are highly significant for achieving the controllable preparation of GQDs while providing guidance for the industrial preparation of GQDs with controllable morphologies and optical properties via gaseous detonation. other: Future work will focus on optimizing these parameters to maximize the efficiency and quality of GQD production and exploring the application potential of GQDs in various industrial fields.

Background: The cyclodextrin-based metal-organic complex (CD-MONT-2) exhibits Pb (II)-rings-based luminescence and water-stable properties. In this paper, it was successfully utilized as a multifunctional material, applied as a fluorescent probe for Ag+ and an adsorbent for Congo red. Methods: X-ray powder diffraction analysis (PXRD), fluorescence analysis (FL), UV-Vis spectroscopy (UV-Vis), Fourier infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and SEM X-ray energy dispersive spectrum (SEMEDS) were employed to study and prove the mechanism Ag2O-involved. Results: The fluorescence intensity clearly decreases as Ag+ solution (1 mM in H2O) is added continuously. At a dose of 1.67 mM, the maximum fluorescence "turn-off" condition is reached, and at 432 nm, the fluorescence quenching percentage is almost 65%. The adsorption capacity of CD-MONT-2 for Congo Red is 22.95 mg/g, with a removal rate of 71.98%. Methyl orange follows with an adsorption capacity of 7.46 mg/g and a removal rate of 22.83%. The adsorption ability of rhodamine B by CD-MONT-2 is poor, the adsorption amount is 6.76 mg/g, and the removal rate is 19.75%. Conclusion: The multifunctional CD-MONT-2 is utilized as an Ag+ probe through fluorescence quenching and naked-eye detection with good sensitivity and selectivity. The max fluorescence quenching percentage is 65% with the Ag+ concentration of 1.67 mM, and the LOD is calculated to be 0.3856 mM. As an adsorbent, we found that the Congo red (anionic dyes) could be efficiently adsorbed. The adsorption performance may come from the mutual attraction of positive and negative charges, and the interaction between CD-MONT-2-OH and Congo red-NH2. The kinetic results indicate that the adsorption process of CD-MONT-2 on CR is more in line with the pseudo second- order kinetic fitting model and is influenced by chemical reactions.

Background: Mercury (Hg) is a highly neurotoxic pollutant present in different environmental matrices. Herein, a simple and sensitive assay is proposed for Hg detection in environmental water samples employing polyethylene glycol monododecyl ether (PGME) stabilized silver nanoparticles (PGME-AgNPs). Methods: The prepared PGME-AgNPs were characterized by absorption, scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and Zeta potential measurements. The addition of Hg(II) to an aqueous matrix changed the color of the sensor, following a decrease in surface plasmon resonance (SPR) band intensity. Results: The detected response was proportional to Hg (II) concentrations and the analytical response comprised a change in absorbance versus concentrations from 4.0 to 24 × 10-8 mol L-1 (0.8 – 4.8 μg L-1) and the limit of detection (LOD) was 4.0 nmol L-1 (0.08 μg L-1). Additionally, the sensor was integrated with the RGB color values of a smartphone, enabling its use as a portable sensor for rapid Hg(II) at a concentration level ranging from 6.0 to 24 × 10-8 mol L-1 (1.2 - 4.8 μg L-1). Spectrophotometric and RGB color value-based approaches were applied for the quantification of Hg(II) in real water samples with satisfactory recoveries ranging from 98.5 to 105%. Conclusion: The proposed colorimetric method with a smart assisted approach was proven a very simple, and quick method, demonstrating practical applicability for on-site Hg screening of aqueous matrices.

Background: Particulate matter poses a significant risk to human health, particularly fine particulate matter, as it is difficult to eliminate and leads to severe health issues. Conversely, urban woody plants are experiencing ambient pollution directly and continuously adjusting to the dynamic contaminants, thereby improving the urban environment for their living circumstances. Thus, studies conducted at the level of individual leaves can offer important insights into the productivity of an ecosystem Method: Leaf samples from three common woody plant species (Acer platanoides, Fraxinus excelsior, and Tilia tomentosa) in Budapest, Hungary, were collected throughout a vegetation phase. After ultrasonic wash-off, the chemical properties of dust deposits on the leaf surface were investigated. Results: Our results showed a higher concentration of wash-off fine particulate from F. excelsior than from A. platanoides and T. tomentosa, and the precipitation, maximum wind speed, and ambient particulate matter content did not demonstrate a significant impact on it. Thus, the fine particulate matter washed off from woody plant leaves involves a more dynamic and complex procedure. The analysis of chemical parameters demonstrated the interaction of particulate matter and the leaves; pH values varied, and the total electric conductivity was significantly higher than the accepted limits. The excessive concentration of sulphate and chloride in wash-off particulate matter indicated significant interference caused by human activities and secondary suspension. Conclusion: Given that F. excelsior is more susceptible to having wash-off fine particulate matter, which can contribute to secondary suspension, the capability of A. platanoides and T. tomentosa to retain fine particulate may contribute to their effects in phytoremediation.

Objective: The increasing environmental pollution from antibiotics poses a significant threat to public health, and this is a critical issue that requires immediate attention. Methods: In this study, a simple and effective surface modification technique was presented using hyaluronic acid-dopamine conjugate (HA-DA) to impart anti-biofouling properties to basin-concave mesoporous carbon (BCMC). The synthesized materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, nitrogen physisorption, and thermogravimetric analysis (TGA). The optimum adsorption performance of the synthesized materials was investigated via adsorption isotherms and kinetics experiments. Afterward, the obtained particles were used as solid-phase extraction subjects for Norfloxacin (Nor) analysis in wastewater. Results: After being quantified by high-performance liquid chromatography (SPE-HPLC), the synthesized BCMC@HA-DA demonstrated an impressive binding capacity of 14.80 mg/g for Nor. Following six adsorption-desorption cycles, the adsorption revercory remained at 81.65%. Conclusion: The prepared BCMC@HA-DA could successfully be concentrated Nor from wastewater, indicating significant potential for addressing environmental biofouling issues.

Background: Essential oils are utilized in various food applications and are a rich source of naturally occurring volatile components. The extraction of essential oils has used conventional techniques for several years, but these methods require a long duration of time, more solvent, and high energy. However, recent advancements have led to novel and eco-friendly techniques that significantly enhance the essential oil yield while minimizing the use of resources. Method: This study describes the recent research on the extraction of essential oils and their components, focusing on microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE). Result: This review explores the instrumentation, mechanism, and applications behind MAE and UAE. It also describes the emerging technologies for the extraction of essential oils, along with their optimized conditions. Conclusion: These techniques represent a more sustainable and efficient approach for the extraction of essential oil from various plant sources, aligning with the principles of green chemistry.

Background: Flavonoid is a type of active constituent in herbs and always used as the quality control markers of herbal medicines. Owing to the extensive diversity of flavonoids, numerous reference compounds are necessitated for the analysis of flavonoids, and some are usually very expensive, which engenders challenges in the analysis of flavonoids in herbal medicines. Consequently, the development of a simple, rapid, and reference compounds saving method is important for the determination of flavonoids in herbal medicines. Objective: In order to develop a high-performance liquid chromatography (HPLC) method for the determination of 5 flavonoids (mangiferin, hesperidin, baicalin, buddleoside, and rutin) in five herbal medicines (Anemarrhenae rhizome, Sophorae flos, Citri reticulatae pericarpium, Scutellariae radix, and Chrysanthemi indici flos) with rutin. Methods: Five herbal medicine samples were prepared according to the Chinese Pharmacopoeia which includes ultrasound and reflux methods. The separation of the sample was performed on a PoroShell 120 EC-C18 (4.6 mm×100 mm, 2.7 µm) by gradient elution with 0.1% formic acid and acetonitrile at a flow rate of 1.0 mL/min. The wavelengths were set as follows: Anemarrhenae rhizome (363 nm), Sophorae flos (256 nm), Citri reticulatae pericarpium (236 nm), Scutellariae radix (263 nm), Chrysanthemi indici flos (354 nm). Results: The method validation showed that the established HPLC method was accurate and stable for quantitative analysis of flavonoids in five herbal medicines. The comparative analysis revealed that the determination results of the current HPLC method and Chinese Pharmacopoeia method are consistent, exhibiting less than 1% relative error. Remarkably, the developed HPLC method needs one cheapest reference compound (rutin) and costs 8 min for sample HPLC analysis. Conclusion: The developed HPLC method for quantitative analysis of five flavonoids in five herbal medicines is simple, rapid, and reference compound saving, which provides a good alternative method for quality control of flavonoids in herbal medicines.

Background: Vitamins are needed for the healthy functioning of the body. When these vitamins are not in sufficient amounts in the body, they are usually taken externally with pharmaceutical preparations. Taking vitamins into the body in the right amounts is possible by analyzing the amounts in pharmaceutical preparations with validated methods. Methods: In this study, a fast, simple, easily applicable, and selective normal-phase HPLC method was developed for the simultaneous determination of fat-soluble A, D3, E, and K1 vitamins in pharmaceutical preparations from syrup and tablets. Separation of the vitamins was carried out on a Zorbax CN column (250 x 4.6 mm, 5 µm) using a mixture of hexane-isopropyl alcohol (98:2, v/v) at 30°C column temperature and 1 ml/min flow rate. The detection wavelength is 280 nm. The developed method has been validated according to ICH Harmonised Tripartite Guideline Validation of Analytical Procedures: Text and Methodology Q2(R1) rules. Results: Calibration graphs are linear over the range of 10-1000 µg ml-1 , 1-50 µg ml-1 , 10-2000 µg ml-1 , 0.5-20 µg ml-1, and the limit of detection values were found to be 1.496, 0.280, 1.388 and 0.040 µg ml-1 for A, D3, E and K1 vitamins, respectively. Relative standard deviation values, which express within-day and between-day repeatability, were found below 2.54%. Average recovery values were also found at about 100.28, 101.46, 100.65, and 100.29% for A, D3, E, and K1 vitamins, respectively Conclusion: The developed and validated method was successfully applied to the simultaneous analysis of fat-soluble vitamins A, D3, E, and K1 in pharmaceutical preparations in syrup and tablet form.